Chapter 39 Notes
The Endocrine System
The endocrine system is made of glands that release their products into the bloodstream. There products broadcast messaged throughout the body.
Hormones are chemicals that travel through the bloodstream and affect the activities of other cells. They bind to specific chemical receptors on those cells. Cells that have receptors for a particular hormone are called target cells. If a cell doesn't have a particular receptor or receptors that don't respond to the hormone, then the hormone has no effect on it.
Glands are organs that produces and releases a substance, or secretion. Exocrine glands release their secretions through tube like structures called ducts. These include sweat, teas, and digestive juices. Endocrine glands release their secretions (hormones) directly into the bloodstream.
Made of lipid called cholesterol
Cross cell membranes easily
1. Enters cell by passing though its membrane
2. Binds to a steroid receptor proteins (target cells only) forming hormone-receptor complex
3. Hormone receptor complex enters nucleus of cell binds to DNA control sequence
4. Binding initiates transcription of specific genes to mRNA
5. mRNA moves into the cytoplasm and directs protein synthesis
Hormone-receptors complexes work regularly
Steroid hormones affect gene expression directly, produce dramatic changed in cell and organism activity
Made of proteins, small peptides, and modified amino acids
Generally cannot pass through cell membrane
1. Binds to receptor on cell membrane
2. Binding activated an enzyme on inner surface of cell membrane
3. Enzyme activated secondary messaged that carry the message of the hormone inside the cell. Calcium ions, cAMP (cyclic adenosine monophosphate), nucleotides, and even fatty acids can serve as second messengers.
4. Once released, these second messengers activated a wide range of other cell activates
Other than red blood cells, all cells have been shown to produce...